\begin{tikzpicture}
    \pgfmathsetmacro{\R}{1.5}

    \begin{scope}[xshift=3.5cm,yshift=3.3cm]
        \tkzDefPoints{0/0/r1, \R/0/r2}
        \tkzDrawSegments[xianduan={below=0pt}](r1,r2)
        \tkzLabelSegment[above](r1,r2){$R$}
    \end{scope}

    \tkzDefPoints{0/0/O, 5/0/A, 2/3.5/B}
    % \tkzDefPoint(50:5){B}
    \tkzDrawSegments(O,A  O,B)
    \tkzLabelPoints[below](A)
    \tkzLabelPoints[left](B,O)

    % 1
    \tkzDefLine[bisector, normed](A,O,B)  \tkzGetPoint{c}
    \tkzDefPointOnLine[pos=5](O,c)  \tkzGetPoint{C}
    \tkzDrawSegment(O,C)
    \tkzLabelPoints[right](C)

    % 2
    \tkzDefShiftPoint[O](90:\R){D}
    \tkzDefLine[parallel=through D](O,A)  \tkzGetPoint{E}
    \tkzDrawSegment(D,E)
    \tkzLabelPoints[left](D)
    \tkzLabelPoints[right](E)

    \tkzInterLL(D,E)(O,C)  \tkzGetPoint{F}
    \tkzLabelPoints[above](F)

    % 3
    \tkzDefShiftPoint[F](270:\R){G}
    \tkzDrawCircle[thick](F,G)
    \tkzDrawSegment(F,G)
    \tkzLabelSegment[right](F,G){$R$}
\end{tikzpicture}

